As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAXI OUT LEFT BRAKE WILL NOT RELEASE. PASSENGERS DEPLANED ON TAXIWAY. MTC DETERMINED PARKING BRAKE WAS NOT RELEASING COMPLETELY. A/C RETURNED TO GATE AND PARKING BRAKE DEFERRED PER MEL 32-7. A/C RETURNED TO SERVICE. INSTALLED PARKING BRAKE KNOB.